At least 20 people have been killed and more than two dozen injured in a mass shooting at a shopping mall in El Paso, Texas. A gunman armed with an AK-47-style assault rifle opened fire on victims as young as four months old in Cielo Vista mall at around 10am local time. Most were shot in a Walmart store within the shopping complex before the shooter was detained at the scene, police said. US media outlets named Patrick Crusius, 21, from Allen in Dallas, Texas, as the suspect. A CCTV image showing a man walking into the mall brandishing an assault rifle was released by police. He was wearing a dark T-shirt and ear protectors. Texas, Gov. Greg Abbott said "20 innocent people from El Paso have lost their lives and more than two dozen more are injured". "We as a state unite in support of the victims and their family members. We want to do all we can to assist them," he said. Police said 26 people were injured, most of them being treated at area hospitals. Various news reports said the ages of victims being treated at hospitals ranged from two to 82 years. This CCTV image obtained by KTSM 9 news channel reportedly shows the gunman entering the Cielo Vista Walmart store in El Paso on august 3, 2019. Credit: COURTESY OF KTSM 9 Police probe anti-immigrant manifesto "The scene was a horrific one," said El Paso Police Chief Greg Allen, who added that many of the injured had life-threatening injuries. He said police also had found an anti-immigrant manifesto that may have been written by Crusius and posted online - one reason it was being investigated as a hate crime. "Right now we have a manifesto from this individual that indicates to some degree, it has a nexus to potential hate crime," Mr Allen said. In the document, the author expressed support for the suspect in the Christchurch mosque shootings, in which 51 people were killed. A police officer stands outside a home in Allen, Texas, believed to be associated with a mass shooting Credit: AP Asked during a CNN interview about reports of disturbing online posts made by the suspect, Texas Attorney General Ken Paxton said he would not be surprised in any way. "I think those can help shed light on why he did it," Paxton said. "They are still interviewing him." El Paso, a nine-hour drive from the Dallas area, lies on the Rio Grande River that marks the US border with Mexico. It has a population of 680,000, of which 83 percent are of Hispanic descent, according to US census figures. Mexico's President Andres Manuel Lopez Obrador said three Mexicans were among the dead. Six Mexicans were wounded. It was the eighth worst mass shooting in modern US history, after the 1984 shooting in San Ysidro that killed 21 people. Trump reacts to shootings In his first reaction to the shooting, Donald Trump, the US president, wrote on Twitter: “Terrible shootings in ElPaso, Texas. Reports are very bad, many killed. Working with State and Local authorities, and Law Enforcement. Spoke to Governor to pledge total support of Federal Government. God be with you all!” He later called the attack "an act of cowardice". Today’s shooting in El Paso, Texas, was not only tragic, it was an act of cowardice. I know that I stand with everyone in this Country to condemn today’s hateful act. There are no reasons or excuses that will ever justify killing innocent people....— Donald J. Trump (@realDonaldTrump) August 4, 2019 "Melania and I send our heartfelt thoughts and prayers to the great people of Texas." It was initially reported that a man began shooting in the car park at the mall before moving inside. One witness said he saw at least one person inside the store with a fatal head wound, and he saw shoppers in bloodied clothes. Videos posted on social media showed customers at one store being evacuated with their hands up. “We heard shots and saw smoke,” said Victor Gamboa, 18, who works at the McDonald’s inside the Walmart store where the shooting took place. “I saw a man on the floor full of blood. He appeared to be dead. It happened very quickly.” 'He was just shooting randomly' Shoppers fled for their lives, including Kianna Long who was at the Walmart with her husband when they heard gunfire. "People were panicking and running," Ms Long said. "They were running close to the floor, people were dropping on the floor." She and her husband sprinted through a stock room at the back of the store before sheltering with other customers in a steel container in a shipping area. “Hands up! Hands up!” Videos show people being evacuated from the Cielo Vista Mall in El Paso, Texas amid the mass shooting at a Walmart that killed at least 20 people and left more than two dozen others injured. https://t.co/WG7XeQua9npic.twitter.com/tyuatkD2up— ABC News (@ABC) August 4, 2019 One woman, who gave her name as Vanessa, said she had just pulled into the Walmart parking lot when the shooting began. "You could hear the pops, one right after another and at that point as I was turning, I saw a lady, seemed she was coming out of Walmart, headed to her car. She had her groceries in her cart and I saw her just fall," she told Fox News. "He was just shooting randomly. It wasn't to any particular person. It was any that would cross paths." Graphic video from the scene posted on social media showed what appeared to be dead bodies and wounded victims. Tales of heroism also emerged. Kendall Long (L) comforts Kianna Long (R) who was in the freezer section of a Walmart during a shooting incident, in El Paso Credit: Rex Officers said the mall was packed with back-to-school shoppers. El Paso police Sgt. Robert Gomez said the store was packed with as many as 3,000 people during the busy season. In a statement, Walmart said: “We’re in shock over the tragic events at Cielo Vista mall in El Paso. We’re praying for the victims, the community and our associates, as well as the first responders.” Oscar Collazo, a restaurant manager, said: “We never thought it would be so close to us this time. You see it on the news all the time, but you don’t think it could happen here until it does.” In a statement, Mr Abbott said El Paso had been “struck by a heinous and senseless act of violence”. “Our hearts go out to the victims of this horrific shooting and to the entire community in this time of loss,” he said. El Paso, which has about 680,000 residents, is in west Texas across the border from Juarez, Mexico. Local media said there was such an overwhelming response to an appeal by the police department for blood donations to help the wounded that long lines formed at medical centers, some of which had to tell would-be donors to come back on Sunday. Law enforcement agencies respond to an active shooter at a Wal-Mart near Cielo Vista Mall in El Paso, Texas, Saturday, Aug. 3, 2019. Credit: AFP Some people handed out bottled water and slices of pizza to those still waiting in line. Democrat candidates demand gun limits Beto O’Rourke, the Democratic presidential candidate, abandoned a campaign event in Las Vegas to return to El Paso, his home town. Earlier, he spoke at a labour forum, telling the crowd the shooting shattered any illusion that gun reform will “come of its own accord” in the US. “We know that there’s a lot of injury, a lot of suffering in El Paso right now,” he said. El Paso is one of the strongest places in the world—and if there were ever a moment to be strong, it's this one. Strong for one another, for the families who have lost somebody, and for the first responders. Please go to https://t.co/ecw9y18OSP to support our community. pic.twitter.com/FFgLPbXNIY— Beto O'Rourke (@BetoORourke) August 3, 2019 The shooting took place within days of two people being shot and killed at a Walmart branch in Southaven Mississippi. "It's not just today, it has happened several times this week. It's happened here in Las Vegas where some lunatic killed 50 some odd people," Vermont Sen. Bernie Sanders said as he and 18 other White House hopefuls were in Nevada to address the nation's largest public employees union. "All over the world, people are looking at the United States and wondering what is going on? What is the mental health situation in America, where time after time, after time, after time, we're seeing indescribable horror." Mr Sanders blasted RepublicanSenate leadership for being "more concerned about pleasing the NRA than listening to the vast majority of the American people" and said that Mr Trump has a responsibility to support commonsense gun safety legislation. Mexican people pray on the US-Mexico border, after a shooting took place at a shopping centre in El Paso Credit: Rex Former Vice President Joe Biden said he tried to call Mr O'Rourke and told reporters, "Enough is enough." "This is a sickness," Mr Biden said. "This is beyond anything that we should be tolerating." He added: "We can beat the NRA. We can beat the gun manufacturers." El Paso and Ciudad Juarez, together with the neighboring city of Las Cruces, New Mexico, form a metropolitan border area of some 2.5 million residents constituting one of the largest bilingual, bi-national populations in the Western Hemisphere. In recent months El Paso has also become one of the busiest entry points for undocumented migrants, especially from Central America, seeking asylum in the United States. On a weekend the city attracts droves of shoppers from Mexico, including from its Mexican sister city Ciudad Juarez, population 1.5 million.